1. Field of the Invention
The present invention relates to systems communicating via serial signals, and in particular, to systems requiring communication of serial signals in forward and reverse directions.
2. Related Art
While levels of integration have increased dramatically in recent years, thereby producing integrated circuits with multiple subsystems integrated within a single die, full integration of complete systems, while potentially possible, is not yet generally practiced. As a result, electronic products, such as cellular telephones, computer systems, digital video systems, etc., rely on “chipsets” in which multiple integrated circuits, or chips, communicate with one another to provide the desired functions and operations. Due to the increased integration of subsystems within each of the chips making up the chipset, it is often necessary to have multiple signals communicated between the chips.
Referring to FIG. 1, for example, in a chipset having at least two chips, a host 10 and a target 12, it is often necessary for the host 10 to transmit high speed data 11a and low speed data 11b to the target 12, while also being able to receive low speed data 11c in return from the target 12. Often, to increase transfer speeds, such data signals 11a, 11b, 11c are transmitted as parallel signals between the host 10 and target 12. Including issues regarding timing among the signals as well as skewing of signal edges, this type of interface tends to be larger, heavier and more costly due to the number of electrical connections, cables and connectors. Accordingly, it would be desirable to have a simpler interface for communications between chips within a chipset.